American Authority?

Does America have the authority to meddle in other countries affairs? In many cases, the answer to this question will change, depending which country is having the affairs. For example, in Iraq, America would have had the authority to meddle in there affairs if they actually had nuclear weapons. Since they don't, there is no reason for America to stay in Iraq. In certain situations, it would be all right for America to meddle with the affairs of other countries. This is only when the country is in some way threatening America. In most cases, America should stop being the police of the world.